Electrical signal-amplifying system



y 6, 1929.. B. F. MIESSNER 3 ELECTRICAL SIGNAL AMPLIFYING SYSTEM Filed July 8, 1926 INVENTOR ATTORN WREI! x? atented My 16, 1929.,

UNITED S A TEs PATENT OFFICE.

BENJAMIN F. MIESSNER, OF SOUTH ORANGE, NEW JERSEY.

ELECTRICAL SIGNAL-AMIPLIFYING SYSTEM.

Application filed J'uly 8, 1926. Serial liovm Llfl.

This invention relates generally to .elec-' trical systems employed for amplification of weak and minor currents suchas signal'currents in radio receiving and amplifying sys' tem .or the like.

The'present invention is in part a continuation of iny application filed August 17, 1925, Serial Number 50,555, wherein a ing and filtering system interposed between. said plate circuit-s andsource of alternat- 4o frequency as that of the source of altcrnat-- radio signal receiving and amplifying system is shown employing three elect-rode vacuum tubes. for amplification of signals, and in which thefilaments of the vacuum tubes are energized directly from a source of. commercial alternating current, while the plate circuits thereof are energized from the same source of current but having a rectifying current.

A radio signal system en1ploying coin-- mercial alternating current, which is usually of cycles, is highly economical when Y compared with storage batteries for supplying the same circuits. However, with the use of the alternating current there is.pro-- duced hum in the translating devices wvhichl is objectionable. This hum is partly due to the use of alternating current employed for energizing the filaments of the vacuum tubes and also partly due to the character .of current employed for energiz-, "mg the plate circuits, which current 15 um- I directional but not entirely steady. More specifically, when employing currentof the character heretofore mentioned for, energizing the 'filament'circuits and the plate circuits of vacuum tubes used in the reception and amplification of signal currents, there is'p'roduced disturbing or extraneous currents of approximately the same order of ing cm'rel'ltemployed for energizing the There disturbing currents being ofa low frequency generally do not noticeably interfere with the transmission and amplificationof signal currents of a high frequency. as for example,-s1gnal currents of radio frequency. However, whenaudw frcqueiu'ysignal currents are beingtrans ferred from one vac'uumtube to another and are ,bein amplified these disturbing current-s, if not eliminated (ii-neutralized,pro-

duce an annoying bum in the translating instruments.

In my co-pending application heretofore referred to and in my co-pendingapplicamay be employed resistances R and .a lead B lmay belextended from a .point between these resistances to provide a rela-:

tion Serial Number 29,859, filed May 13, 1925, I disclosed certain methods and means whereby the disturbing currents may be reduced or eliminated; and the present invention embodies still other means for reduclng or eliminating such disturbing currents. Such other means may be employedv alone or in combination with one or more ofthe means disclosed in the applications above referred to, and'by the use of the present invention it is possible to eliminate entirely any disturbing variations in the sig- I nal currents ultimately received.

The invention is illustrated in the accom-- panying drawing which is a'diagrammatic view of a radio signal receiving and amplifying system corresponding to that shown in my co-pending application, Serial .Number 50,550, having the present improvements incorporated therewith.

Referring to the drawing more particu-' la-rly, VT .and' YT? indicate vacuum tubes connected. in the system for amplification of signal currents at radio frequency; VT indicates a vacuumtube connected in the system as a detector ofthe'amplified signal currents and VT and VT indicate two vacuum tubes connected foraudio frequency amplification of the signal currents rectified by the tube VT The plate circuits of from :1 secondary winding S of the same transformer. The primaryP of transformer PT may be connected toa source of alternating current,v such as usually employed for houselighting, through the meansof plug LP and extension cord therefor as shown. Across the supply leads B and PR ofthe rectified and filtered current there R and lively low potential: current for the plate circuit detector tubeVT r v The secondary winding S and leads A supply unrectified alternating current for heating the filaments of the tubes V1, and VT, while winding Stogether the detector denser with the extension secondary windings S and S? through the medium of leads A supply unrcctifid alternating current of a,v higher potential to the vacuum tube VT. Tube V1 speaker LS and is a more powerful tube than the other amplifying tubes of ,the system. The filament circuit of tube VT is preferably "[Hovided with a current'control resistance 5 while the remainder of the tubes may have their filaments connected directly across the respective supply leads therefor as shown.'

The gridsof all thevacuum tubes are connected to a common grid return GR. There also maybe employed a grid biasing battery (B which may be connected to the filaments through a variable contact X associated with a resistance or potentiometer connected across the filament supply lin'es A.

The'tube-V'l may receive signal energy shown. The tube VT is coupled to tube VT by a radio frequency transformer RF.

Preferably 'a tuning condenser vC is-coniiected across the secondary of the trans-' former REY The tubefiVT is coupled to tube 1 VT through the radio transformer RF A tuning con- C may be'connected abentthesecthe primary of frequent:

ondary of transformer RF ductan'ce' or varionieter V which is connect and the other end'connected to the primary of the output transformer AF fof tube VT. A condenser C is interposed between the grid return GrRv and the last-named end ed to the plate of tube VT 7 of the variometer VU.

The tube VT is coupled to; tube WT? through the audio frequency transformer AF and it will be noted the lead 13 and plate lead of the. primary of this trans former are reversed with respect to the same connections for primary windings of the transformers B1 and AE'-.' The purpose of this' rcvorsal of connections for the primary winding of this transformer will later be fully explai-nd- A high resistance B may be connected across the secondary winding of grid, filament circuit of tube VT about the V secondary oft 'ansformerAF transformer AF l transformer AFR The output't ransforme'r AF w for the tube "VT, has an intermediate point Y'of its primary winding connected to the filtered and rectified current supply lead, B.

.Aijack J provided which in conjunction with telephone plug 'TP and connections 7 shown may be employed for connecting the.

HT about the secondary of liead telephones 'VVith the plug TP connections shown serves to connectthe It should be here mentioned that while the system disclosed the drawings shows 'ceris intended for operating a loud understood that such .ments, and the variation it will be seen that the re-' moved, the ack J infconjunetion"with the 'arisin vacuum tubes VT and VT. turbing currents arising invacuuintubeVT are more or ,less efliciently passed on: to vacuum tube'VT and amplified; The distain and preferred means and connections for separately connecting the loud-speaker and head telephones to the system, it is to be means and connections are not "entirely essential to the use and operation of the disturbing current neutralizing means or couplings disclosed.

"As before stated the present invention relates to reducing or neutralizing the disturbin'g currents arising through the use of alternating current of a low frequency for ener+ 'gizing the filaments of the vacuumtubes employed, and filtered alternating current for the plate circuit of .said' tubes. I neutralization of these disturbing currents is brought about by the coupling means between the vacuum tubes employed in thesys- -ten1 andheretofore described. a; Before proceeding with a description of and also through the use of rectified The reduction or i steady plate circuit cur rents resulting from therectification and -'fil tration of an alternat ing current; the varying potentials, alternately positive andnegative, across the terminals of the filaments -due to the alternating current supplyfor heating the filaoftemperature of the filaments which is in eonsonan'ee with the alternating heating current, and which i'csultsm a varying electron emission by the filaments at double "the. frequency of the alt rnating currents. Since .the'usual frequencyof an available alternating current supp? is .60 per second,

' i'sturbing currents resulting from thecondition's-I have heretofore outlined are of 'aneiitremely low fre quency compared to tlie'radio frequency cur- "rents-of the receiver andiare rather low in frequencycompared to the average signal currents, present inthe audio frequency. portion of the system. Very littleor no diflicnlty' therefore arises in vacuum tubes ,VT

and V I and their associated circuits lbecause the radio frequency transformers which con,-

ve tu yfithe cur rents through and beyond these pass to a. negligible degree only, thedisturbing currents. The difficulty" begins in the detector tube'VT whereith audio .1,

frequency -transformer Ali inore orfless efficiently passes forward disturbing currents g in this tube. These disturbing currentsv are subject to double amplification in r'ents arising in a system of the character variations will ,be carried over to the sec-" .ondaryof transformer AF and thence" to described are reduced or neutralized will now follow: It will be' noted that I provide in theoutput circuit of radio frequency amplifier tube VT a high frequency path' through the variable inductance VL forming the primary of radio frequency trans- -former RF and condenser C'*; and a low frequency path through the upper part of.

the primary of audio frequenc transformer AF. The-result is that high requency currents passing through this tube continue on in the regular manner to the detector tube,

while low frequency currents resulting from the disturbing conditions I have heretofore described act upon the audio frequency transformer AF. I The connections to the pri mary Winding of the transformer AF are such that currents which flow from the lead B through the upper and lower partsof the primary winding oppose one another.

It will also be noted that leads of the primary of the transformer AF are reversed,

the connections to this transformer, beingsuch that Variations in the plate circuit of the tube VT produce similar but opposite palr -iations. in the grid circuit of the tube In operation the alternating-heating current inthe filament of'tube VT produces disturbing variationsjn the plate circuit of this tube and these variations together with disturbing variations in the plate circuit of this tube which are caused by the somewhat unsteady character of potential supplied to the plate by the rectifier and filter, are czirried over through thetransforrn'er AF- to the grid circuit of the tube VT. Because of the reversed connections of the transform- (bl-"AI the resulting variations inthe grid potential of the tube VT are such as will tend to .producein the plate circuit of the tube VT variations which areopposed to variations arising in theplate circuit of tube i v V VT" because of the alternating current in its filament-amltlie unsteady source of plate current. If these variations in thepotential o l the grid of tube VT completely neutralized the disturbing variations arising in tube i VT it is obvious that no disturbing variations would be present in the lower art of the primary of transformer AFF. -urrent in the upper part of the primary of-transfornu-r AF will besubjcct to disturbing variations arising in tube VT and these lthe-gridof tube VT, The connections to the upperpart of transformer AF are such that the effect of variations arising'in tube- VT. .las carried outer-the gridpf tube VT is to -op'pose disturbing variations arising in tube VT. It will thus be seen that the disturbing variations arising in tubes VT and VT are used to op ose disturbing variations arising in tubes T and VT.

In general practit e it will often happen that disturbing variations arising in tube VT and carried over throughtransformer .A F to the grid of tube VT will more than neutralize the disturbing variations arising in tube V T. This is because tube VT actsto amplify variations in potential of its grid. In point of practice,therefore the current in tlu'i. lower part of transformer Al -will vary in phase with variations in potential of the grid of tulwV'l. The e'lfect of variationsin the upper and lower parts of the pr-ianary of transformeruXF will be additive in respect to one another and .each will serve to increase the elfect of the other in causing variations in potential in.tl1e'grid of tube V As the tube VT is a more powerful tube than tubes VT and VT? the disturbng ell'ccts arising in tube VT willbe correspondingly greater than those arising in tubes V T and VT and the increased variations in potential in the grid of tube VT will be required to neutralize completely the tions of potential on the grid of tube VT.

The potentiometer connected'across the filament supply mains A and its adjustable contaet X form an additional means for effecting a reduction in the hum; lVheIi the contact X is at some point ofthe potent'iom eter resistance other than the midpoint,

it will besubjectcd to an alternating potential relative to the midpoint and relative to the inidpoints ofthe filaments of the several tubes. side of the midpoint this alternating potential will be opposite in phase'to the alter- With the contact X at one nating potential to which it would be sub jccted if-connected to a point at the opposite side of the midpoint and these alternatingpotentialsmf the contact X, relative t6 the midpoint. will increase. as'fthe point X is moved farther away from the midpoint. Inasmuch as the contact X- is connectedto the grids of the several tubes and these grids are therefore subjected to the alternating potential of the point X it is apparentthat by. 'a lj1isti1ig the contact X along the potentiometer thealternating potent-ial impressed on the grids may lie varied "both in amplitude and in phase. This alter nating potential on the grid is superposed on the alternatingpotential applied to the grid through the coupling from the preceding tube, and by varying the amplitude and phase of this superposed otential', 1t

is possible to vary the amount of hu'm neutralizing current which is fedfrom one tube to the succeeding tube and in this man.-.

er reduce the hum current in the output circuit. v

In those systems hum is apt to occur in when they are plugged in, ar'y'of transformer AF where an audible across the seccnd- I may if desired provide a means whereby the'plugging in of these headphones will seiwe to short circuit the upper part'of the, primary oftiansforiner AF thus eliminating from the secondary circuit of the transformer AF disturbing effects arising in tube VT.

While I have shown and described my new tralizing means for disturbing or extraneous I currents inconnectio'n with a radio signal receiving and amplifying 'systemit is to be understood that my invention in its broader aspects can be utilized in other and similarsystems and that I do noF-int-cnd to limitmy invention to usein the shown.

Ielaimz- 1. A signal current. amplifying system. having two vacuum tubes 'arra-ngedfor sue articulan system cessive amplification of signaling currents.

' which vary at audio frequency in the plate.

circuit of each tube, a source of current supply for energizing a circuit of each of said tubes and tending to cause'periodic disturbin variations in the plate circuits of said tu es, a coupling between the plate circuit of one of said tubes, and the grid-circuit of the other of said tubes, said' coupling being so arrangedthat the variations produced in the grid circuit by the diSturbi'ngQVa-riations in 'the plate circuit'which is coupled thereto, neutralize the .variations in 'the plate circuit of said-other tube.

2. A m-iilti stage signal'current am lifying system employing a three electro era dio frequency tube'and a plurality of audio;

1 frequency. tubes, adapted successively to amplify signaling current, a sourc'e of unsteady potential forsu-pplying current to said tubes and tending to produce periodic current variations in the plate circuits of 'couplings'between the grid circuit-of each tube and thebeing so arranged that the. eriodic variations from the plate .circuit 0 the preceding tube-are impressed on the grid circuit of the succeeding tube, in

such a way as to oppose variations- -1n the.

plate circuit of the succeeding tube, "and a coil in the'pl'ate circuit. of the radio frequency tube,lpositionedi nductive relation to one of couplings and so related; to said coujpl irg that the periodic I circuit/of said radio frc, encytube will act rte-decrease periodic va iations in the. plate, circuit oft-he last of said 1 audio frequency.

the headphones 'HT- said tubes,

plate circuit of. the preceding, tube, oneof said couplin vprjiati'ons in the plate 3. A. multi-stage signal current amplifying system employing a plurality of'audio frequency 'plify signaling current, an alternating current supply circuit for heating the filaments of said tubes and tending to produce'periodic current variations in the plate circuits of saidtubes, couplings between the grid tubes adapted successively to amcircuit of each tube and the plate circuit of i which are subject to disturbing current variiitions of similar freq 'means for reversing the p I tions in the plate circuit of one of said tubes .and applying said reversed variations to tlie .grid' circ it of a succeeding tube, whereby ency and v phase,

the preceding tube, one of said couplings aseof such variathe distur ing current variations in the plate oircuit of a tube succeeding said second tube ar'ejreduced, and adjustable means for varying said reversed variations.

-5. In a signal amplifying system-employing vacuum tubes connected in cascade, each haying a plate and grid, a source of fluctuating potential for energizing for operation a circuit of each tube so connected to cause disturbing current variations of similar frequency and phase in the plate. circuits of "said tube's, a transformer between adjacent,

oled for reversing the phase ofsuch tubes variations in the plate 'cireuit'of one of'the tubes and applying the reversed variations to the grid circuit pf another of the tubes so as to'reducethe plate current variations iirsaid other tube and adjustableuneans for varying the magnitude'andphase bf'said re-' versed variations;

.6. In a signal ciirrentamplifying systemloying vacuum tubes connectedin casca e, each having a plate :and grid, a source of fluctuating potential for,energizing-foroperation a circ'uit'of each tubeand'tending' to cause disturbing .-current variations of' g similar frequency and phase in the plate circuits of said-tubes, meansfor reducing the plate circuit of one of the ltubes and applying the. reversedvariations to thegrid circuit of another ofjsaid. tubes, and'i'means ifor superposing on themeversed variations other variations of'similar frequency;

said disturbing variations comprising'nieans for reversing the'pliaseofsuch variations in of fluctuating potential for energizing for operation the circuits of each tube and tending to cause disturbing current variations 1n the plate circuits of the tubes, and means for reducing said 'disturbing variations comprising means for reversing the phase of suchvariations in the plate circuit of one of the tubes and applying the reversed variations to the grid circuit of, another of said tubes, means or superposingon the reversed variations other variations of similar frequency, and means for varying the phase and amplitude of said superposed variations. 8. A multistage electrical amplifyin system comprising a pair of three electro e audio frequeney'tubes arranged for successive single tube stages of amplification, means for supplyingcurrent of varying potential for energlzing for operation one of the circuits of eachof said tubes, said varying potential tending1 to cause disturbing current variations in t e plate circuits of said tubes, and means for reducingv saidplate current variations comprising an inductive coupling between said tubes, said coupling comprising primaryand secondary windings so arranged and'connected with the tubes that variations in the plate current from one tube are reversed and the reversed variations are impressed on the grid of the other tube in such a manner as to'oppose or suppress the disturbing current variationsin the plate circuit-of said other tube.

9. In an amplifier system having a plurality of audio amplifier tubes including an output tube, audio coupling units between the output circuits an input circuits of electrically adjacent audio tubes, and means for energizing the filaments of said tubes from a source of alternating current whereby the space current of the several tubestends to vary in phase accord throughout said system, one of the intermediate audio coupling units being so poled that by its in;

fluence on the grid of the next succeeding tube the space current of said output tube due to transferred hum energy-tends to varyin phase opposed to said first tube, whereby the output circuit of the last tube is substantially free of variations produced by energization from saidsource.

10. In an amplifier system rality ot'audio amplifier tubes including an output tube, audio coupling units between the output circuits and input circuits of electrically adjacent audio tubes, means for onergizing the filaments of said tubes from'a source of alternating current whereby the space current of the several tubes tends to vary in phase accord throughout said system, one of the intermediate audio coupling units being so poled, that by its influence on the grid of the next succeeding tube the havinga pluf space current of said output tube due to transferred hum energg tends to vary in phase opposed to said rst tube, and means tor varying the amplitude of the humenergy transferred through said-intermediate audio coupling unit, whereby the output circuit of the last tube is substantially free of variations produced by energization from said source. 4

Signed at New York, in the county of New York and State of New'York, this 1st day of July; A. D. 1926.

BENJAMIN r. MIESSNER; 

